The present invention generally relates to devices for controlling pressure within pneumatic tires and, more particularly, to an improved remotely controlled valve system through which a vehicle tire may be inflated or deflated.
In the operation of wheeled vehicles carried by pneumatic tires, it is frequently desirable to control the inflation pressure within the tires for optimum operational efficiency of the tires and the wheeled vehicle under various operating and road conditions. The adjustment of inflation pressure to fit the particular operating and road conditions extends the tread life of the tires, is a prudent anti-skid precautionary measure, provides blow-out protection, and is justifiable for other safety and economy reasons.
Inflation pressure control is especially important in the operation of large aircraft. For example, optimum tire performance may be obtained using relatively high inflation pressure for take-off, and relatively low inflation pressure for landing. These desirable inflation levels may be variable depending upon weather and runway surface conditions. Further, and especially as applied to the large transport and tanker aircraft, large changes in the gross weight of the aircraft may occur during its mission, such as by personnel or equipment deployment or by inflight transfer of aircraft fuel. Suitable control of the inflation pressure of the tires of the aircraft will provide proper reduced pressure consistent with the landing weight of the aircraft upon termination of the mission. When landing on unimproved airfields, control of the inflation pressure affords maximum flotation capability to the aircraft, and the footprint size is optimized for improved ground control and braking capability on any runway surface. Tire tread life may be extended by as much as 100% by judicious control of the tire inflation pressure.
Systems for effecting and controlling inflation and deflation of pneumatic tires on a vehicle while the vehicle is at rest or in motion are known in the prior art. Representative of such prior art are the systems disclosed in U.S. Patents to Williams (U.S. Pat. No. 2,685,906) and Kress (U.S. Pat. No. 2,747,640). The system of the Williams patent employs inflation pressure control apparatus mounted on the exterior of the wheel hub, whereas the system of the Kress patent provides apparatus mounted in the wheel axle. The systems of both patents incorporate a check valve aligned with and displaceable by a plunger. Pressurized air is used to drive the plunger to open the check valve as well as to inflate the tire.
More recently, a system has been devised by the applicant herein and disclosed in the application cross-referenced above which uses a plunger actuated by an electrical solenoid, as opposed to a plunger actuated by air, to open a poppet valve for routing pressurized air to inflate the tire. Employment of a solenoid-actuated plunger contributes to a reduction of the overall complexity of the apparatus compared to those disclosed in the two mentioned patents and enhances its reliability in terms of the need for fewer air pressure seals. The apparatus disclosed by applicant in his cross-referenced application is believed preferable over those of the cited patents in terms of its construction and function.
However, it has recently been recognized that there are areas in the design of applicant's apparatus that need to be improved. First, the space occupied by the poppet valve and inner manifold housing seems excessive and thus an alternative construction in this area of the apparatus which requires less space would be desirable. Second, the size of the outer manifold housing and its deployment on the exterior of the hub cap has drawbacks in terms of its bulkiness and exposure to possible damage. Third, the apparatus fails to provide any means to monitor the inflation pressure of each tire without actually actuating the solenoid-operated plunger to open the poppet valve in order to establish communication between the tire and the pneumatic controller of the system.